Week 2 Lecture 2 - natural selection

Question 1

Is evolution like a chain or a branch

Answer 1

branch

Question 2

What is adaptation

Answer 2

function if a trait that has been evolved by NS

Question 3

What are the 4 core principles of natural selection?

Answer 3

• variability
• heritability
• surplus offspring
• non-random survival and reproduction

Question 4

What is variability?

Answer 4

• individuals of species differ, this gives NS something to act on
• variability can be so good that it becomes hard to determine what distinguishes a species

Question 5

What is heritability?

Answer 5

variability has to be transmitted generation to generation (vertical transmission)

Question 6

Where does the main source of heritable variability come from?

Answer 6

genes

Question 7

Do genes blend?

Answer 7

no

Question 8

What is surplus offspring?

Answer 8

more offspring produced than can be supported by the environment (carrying capacity)

Question 9

What is non-random survival?

Answer 9

complexity could not have arose by chance
survival and reproduction isn’t random
individuals with traits better suited to the current env., on average, are more likely to survive and produce viable offspring

Question 10

What are the 4 Fs of fitness?

Answer 10

• fighting
• feeding
• fleeing
• reproduction

Question 11

What is fitness?

Answer 11

the differential survival reproduction of individuals

Question 12

Do organisms always perfectly adapt to an env.?

Answer 12

no
the optimum solution can change –> getting from one to the other world would involve a reduction in fitness

Question 13

What is genetic drift?

Answer 13

random change due to change

Question 14

What factors can affect genetic drift?

Answer 14

• pop. bottleneck
• founder effects

Question 15

What did Mendel do?

Answer 15

cross-breed peas to show that genes don’t blend

Question 16

What is the law of segregation (Mendel’s 1st law)

Answer 16

every individual has 2 copies of the “particles” for a trait
pairs of these particles separate and get passed into different sex cells
they unite with another particle after fertilisation and form a zygote

Question 17

What is the law of independent assortment (Mendel’s 2nd law)?

Answer 17

particles for different traits assort independently

Question 18

Why do some traits appear to blend?

Answer 18

• there is more than 1 gene for the trait
• codominance
• incomplete dominance

Question 19

What is locus?

Answer 19

genes occupy different positions on a chromosome

Question 20

What are the different effects that genes can have on the phenotype?

Answer 20

• one gene, one effect
• polygenic: many genes one effect
• pleiotropic: one gene, many effects
• polygenic and pleiotropic

Question 21

What do structural genes code for?

Answer 21

proteins

Question 22

What is a gene?

Answer 22

a segment of DNA specifying the sequence of amino acids in a protein

Question 23

What are 4 functions of proteins?

Answer 23

• structural functions e.g., collagen
• enzymes e.g., lactase
• hormones e.g., insulin
• regulatory proteins

Question 24

What is epigentics?

Answer 24

non-genetic changes in gene expression

Question 25

How can gene function be studied?

Answer 25

directly or indirectly

Question 26

What are some examples of indirect gene study?

Answer 26

twin studies

Question 27

What are some examples of direct gene study?

Answer 27

CRISPR, gene sequencing, SNP

Question 28

What is neo-Darwinism?

Answer 28

fusion of Darwinian evolution by NS and Mendelian inheritance

Question 29

What does Neo-Darwinism believe about evolution?

Answer 29

populations evolve not individuals

Question 30

NS is one force for changing allele frequencies in populations. What are some others?

Answer 30

• mutation
• gene flow
• genetic drift (inc. founder effect)
• non-random mating (i.e., artificial selection)
• meiotic drive (selfish genes)

Question 31

What is the selfish gene?

Answer 31

selection ultimately acts on genes not individuals

Question 32

What is population genetics?

Answer 32

evolution to a population geneticist –> change in allele frequencies over time

Question 33

What are analogies?

Answer 33

convergent evolution –> independent evolution produces analogous traits
traits that appear similar but evolved separately

Question 34

What are homologies?

Answer 34

adaptive radiation –> similarity by descent
produces homologous traits

Question 35

How can we tell is a trait is homologous or analogous?

Answer 35

comparative method –> phylogenetic history and similar ecological pressures

Question 36

What are vestigial traits?

Answer 36

vestigial traits have lost their function through evolution
e.g., human fear or spiders

Question 37

Are all traits adaptations?

Answer 37

no - not all origin stories are plausible
“Just so stories”

Question 38

What are exaptations?

Answer 38

traits that serve a different purpose than the one they were adapted for

Question 39

what are developmental byproducts?

Answer 39

traits that arise as a by-product for a selected trait somewhere else

Question 40

What are maladptions?

Answer 40

traits can be adaptive in the env. in which they evolved, but not now

Question 41

Can all traits endure phylogenetic inertia and genetic/physical constraints?

Answer 41

no

Question 42

can evolvability be adaptive?

Answer 42

yes